Plants are subject to attack by a great number of pests such as fungi, bacteria, and nematodes. As a result, pesticides have been used to protect crops since before 2000 BC. Historically, elemental sulfur, arsenic, mercury, and lead were applied to crops to kill pests. The 17th through 19th centuries saw the development and use of several natural pesticides (biopesticides), including nicotine sulfate, extracted from tobacco leaves, pyrethrum, derived from chrysanthemums, and rotenone, extracted from the seeds and stems of several plants, such as the jicama vine plant, and the roots of several members of the family Fabaceae. Until the 1940s, arsenic-based pesticides were most commonly used. Beginning that decade, manufacturers began producing synthetic pesticides in large quantities, and their use became widespread. Since 1950, pesticide use has increased over 50-fold, with over 5 billion pounds of pesticide active ingredients being used globally each year.
A primary benefit of pesticide use is controlling pests and plant disease vectors. The use of pesticides has vastly improved agricultural productivity, increasing the global food supply. One study found that not using pesticides reduced crop yields by nearly 10%. Another study found that a ban on pesticides in the United States may result in the rise of food prices, a loss of jobs, and an increase in world hunger levels.
Despite their utility, pesticides have garnered significant attention due to their adverse health and environmental effects. Exposure to pesticides has been linked to a variety of adverse health effects, from irritation of the skin and eyes to more severe effects such as neurological damage, reproductive issues, and cancers such non-Hodgkin lymphoma and leukemia. Studies have also linked pesticide exposure to the development of neurological disorders, birth defects, fetal death, and neurodevelopmental disorders, among other diseases and disorders.
Pesticide use has also been shown to have negative environmental effects. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species. This pesticide drift results in water pollution and soil contamination. Pesticide use has also been shown to contribute to pollinator decline, destruction of habitats, reduced biodiversity and nitrogen fixation, and to threaten endangered species. Furthermore, chlorinated hydrocarbon pesticides are not excreted, but rather dissolve in fats. This results in organisms tending to retain such pesticides indefinitely, resulting in biological magnification, where the chlorinated hydrocarbons are increasingly concentrated at each level moving up the food chain.
With increased environmental and health concerns related to pesticide use, and increased resistance of pathogens and pests to chemical control materials, new chemistries that are effective, environmentally safe, and non-toxic to humans are needed.
Plants have evolved highly effective mechanisms for resistance to pests. When a plant is discovered to produce one or more substances capable of controlling pests, an extract or isolated compound from the plant may be utilized as a biopesticide. Biopesticides are typically either microbial or biochemical in nature, and may have a broad range of pest control capabilities including herbicidal, insecticidal, nematicidal, termiticidal, bactericidal, antimicrobial, and fungicidal properties. Microbial biopesticides include entomopathogenic fungi, Trichoderma species, Ampelomyces quisqualis, Bacillus subtilis, beneficial nematodes, and entomopathogenic viruses. Various materials, including fungal and plant extracts, have also been described as biopesticides, including plant-derived products such as alkaloids, terpenoids, phenolics and other secondary chemicals, and certain vegetable oils such as canola oil.
Biopesticides may be applied in a manner similar to conventional chemical pesticides, and have already established themselves on a variety of crops. Unfortunately, many biopesticides are highly specific, requiring an exact identification of the target pest and/or pathogen. Biopesticides also vary considerably in efficacy.
Currently, biopesticides account for only about 3% of the total pesticide market, with a value of $750M (2008). There is a need to develop safer and more sustainable pesticides that are efficient and have a broad spectrum of use. Further, there is a need for sustainable pesticides that can be utilized in both the organic and conventional markets.